The invention relates to a hydraulic power wrench.
In known hydraulic power wrenches, the cylinder of the cylinder unit is fixedly connected to the wrench head, whereas the piston presses against a support arm, which is rotatably connected with the wrench head (U.S. Pat. No. 4,440,046). The wrench head is set on the screw to be turned, while the support arm is set against a stationary abutment to divert the reaction forces occurring during the screwing. The wrench head contains a ratchet to effect a rotational pulling of the screw only in the intended direction of rotation, but not in the opposite direction, during the translational movements of the piston of the cylinder unit.
Moreover, hydraulic power wrenches are known that are not provided with a support arm pivotable around the axis of the wrench head. With these power wrenches, the support on the stationary abutment is effected by the end of the piston of the cylinder unit pressing directly on the abutment. Also in this case, the cylinder unit is integrally connected with the wrench head.
Power wrenches often have to be set on not easily accessible screws. In that case, the cylinder unit can be hindering when setting the power wrench on a screw. This is particularly true, if the wrench head is of the same width (axially to the screw) as the cylinder unit, since the casing of the cylinder unit requires a fairly large width. In some instances, the wrench head can only be set on half the length of the screw head or even on the outer edge of the screw head only, because the comparatively large volume of the cylinder unit prevents a full setting of the wrench head on the screw for outer impediments.
It is an object of the invention to provide a hydraulic power wrench that can be adapted to the constructional conditions near the screw head to be turned and that is suited for turning screws that are not easily accessible.
The cylinder unit of the power wrench according to the invention is displaceable relative to the wrench head, the direction of the displacement being generally parallel to the axis of the wrench head or the axis of the screw to be turned. When the power wrench is actuated, no force acts in the direction of the guiding track, along which the cylinder unit is displaceable relative to the wrench head, so that it is not necessary to fix the cylinder unit to the wrench head. The cylinder unit may be freely displaceable in the guiding track, however, it is also possible to provide a locking device that has to be disengaged in order to allow a displacement. It is important that the cylinder unit may be displaced in the direction of the axis of the wrench head and that it may be set in different positions.
Preferably, the cylinder unit can be shifted along the guiding track as far as to be completely removed from the wrench head. Thus, it is possible to use the wrench head in connection with different cylinder units that only have to be inserted into the guiding track of the wrench head.
The width of the cylinder unit (in the direction of the axis of the wrench head) is substantially determined by the diameter o the hydraulic cylinder. In order to keep the hydraulic pressure within the cylinder from being too high, the cylinder unit should not be too small of size. Normally, the cylinder head is arranged symmetrical to the central longitudinal plane of the cylinder unit. The movability of cylinder unit and wrench head make it possible to displace the cylinder unit with regard to the central plane of the wrench head, so that the wrench head can be fully set on the screw head to be turned, even if this screw head has a small height.
The wrench head, due to its very narrow width, is lightweight and can also be set in locations that are not easily accessible.
An additional intermediate track provides still greater possibilities of movement and adaptation. This intermediate track also needs only to be inserted loosely into he guiding track of the wrench head and does not require locking. Further, the cylinder unit can be loosely inserted into the guiding track of the track, without having to be locked. Preferably, the guiding tracks of the wrench head and the intermediate track are of the same profile, so that the cylinder casing can be alternatively inserted into the guiding track of the wrench head or that of the intermediate track. Thus, the intermediate track is provided at its opposite ends with two mutually complementary profiles.
Using the intermediate track, it is possible to use several cylinder units at the same time to increase the rotary force. For example, the rotary force needed to loosen a screw may be much greater than the rotary force needed to tighten that screw. If the force of a single cylinder unit is not sufficient, a second cylinder unit can be inserted into the intermediate track, with both cylinder units being operated simultaneously.
If a support arm is used that is supported against a stationary abutment, this support arm is preferably provided at or in a socket wrench that is set on the wrench head. The support arm is substantially of U-shape and it is provided with an outer leg, extending parallel to the axis of the wrench head, against which leg the piston of the cylinder unit presses.
The wrench head can also be used in different angular positions with regard to the cylinder unit, due to the wrench head being adjustable around the centre of the profile of the guiding track. The position of the axis of the wrench head with regard to the abutting element can thus be varied. This allows an adaptation of the device to many screwing situations by simply changing the position of the wrench head on the cylinder unit. Preferably, the profile of the guiding track is integrally formed with the cylinder casing. Also when using a guiding track that allows different angular positions of the wrench head with regard to the cylinder unit, the wrench head can be set on the cylinder unit after having been turned by 180.degree. (upside down), so that the screw can be rotated in both directions of rotation.